M. kansasii is treated using a combination of drugs called antibiotics. As with HIV, in which three drugs are used to help prevent resistance and keep viral load undetectable, M. kansasii must be treated with a combination of drugs to maintain control over the infection.
It can take between two to eight weeks for a patient with M. kansasii to start feeling better upon starting treatment. Because of this, the infection is often treated in a hospital, where resources are readily available to help manage symptoms such as weight loss, fever, and dehydration.
Almost always, M. kansasii combination therapy includes at least two of the following drugs, which are taken for two months:
Rifampin (Rifamate®) or rifabutin (Mycobutin®): Rifampin is actually the preferred choice. However, this drug does not combine well with many protease inhibitors or non-nucleoside reverse transcriptase inhibitors used to treat HIV. If you are being treated for both M. kansasii and HIV, a better option is rifabutin. However, the dose of rifabutin may still need to be adjusted, depending on which anti-HIV drugs you are taking.
Ethambutol (Myambutol®): This antibiotic is active against M. kansasii, but not powerful enough to be used on its own. As a result, it is almost always combined with either rifampin or rifabutin.
Clarithromycin (Biaxin®) or azithromycin (Zithromax®): Both of these drugs are considered to be alternatives if either of the above options are not possible. Test tube studies suggest that these two drugs are effective against M. kansasii. However, there has only been a limited amount of information from clinical trials to prove this.
After two months of therapy has been completed, the patient is usually switched to isoniazid (Nydrazid®) combined with pyridoxine (vitamin B6) . Isoniazid is an antibiotic that is most commonly used as a treatment for tuberculosis (pyridoxine is used in combination with isoniazid to help prevent peripheral neuropathy, a possible side effect of isoniazid). The isoniazid and pyridoxine are taken every day for at least 18 months. If an HIV-positive person is diagnosed with M. kansasii, he or she may be required to continue isoniazid/pyridoxine therapy for life. In some cases, anti-HIV therapy can help improve the health of the immune system. If the immune system improves significantly, stopping isoniazid/pyridoxine therapy is possible.
Prevention
As mentioned earlier in this lesson, it is very difficult to prevent coming into contact with M. kansasii. However, the same medications used to prevent Mycobacterium avium complex (MAC) – once-daily Clarithromycin (Biaxin®) or once-weekly azithromycin (Zithromax®) – may help reduce the risk of M. kansasii infection in HIV-positive people with suppressed immune systems. The risk of developing disease from MAC and M. kansasii is greatest when a patient's T-cell count falls below 50. In turn, most experts recommend starting preventative therapy – called prophylaxis – when the T-cell count falls below 75.
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